This invention relates to electromagnetic relays and more particularly to a unique modular relay.
In a wide variety of applications, a need exists for a compact, subminiature double pole, double throw relay wherein the center contacts are positively latched in one of two positions upon de-energization of the solenoid. For example, in the area of automatic sequence control systems it is highly desirable to maintain the movable pair of relay contacts or terminals connected to either of the two other pairs of terminals upon de-energization of the solenoid windings. If a positive latching arrangement is not employed, the position of the movable contacts may undesirably change upon system shut-down. Also, various safety control systems are presently being employed with industrial machinery which will effectuate shut-down upon occurrence of a fault in the equipment. Forexample, safety monitor circuits are being employed to sense slipping of power press brakes.
Heretofore, solenoid operated relays have been employed to effectuate equipment shut-down upon the occurrence of a fault condition in the brake. Some of these brake monitor systems have permitted reuse of the equipment when the operator merely recycles the main power switch. In order to prevent such unsafe operation, a pair of single throw relays have been interconnected to prevent reoperation of the press. This arrangement requires that corrective measures be taken beyond the mere cycling of the power supply. This solution to the problem is costly since it requires the use of two relays. Also, the space requirements for the monitoring system are substantially increased. No known double pole, double throw, latched relay is available which possesses the unique qualities such as size, cost and amperage rating necessary for these applications.
Heretofore, various forms of latched relays have been proposed. The majority of these relays employ a permanent magnet arrangement to positively retain the movable contact assembly in engagement with one of the pair of fixed terminals. Due to the structural arrangement of these relay assemblies, they have been relatively expensive to manufacture. Latched relays having a sufficient amperage rating for use in the wide variety of control systems of the type discussed above have been relatively bulky in size and therefore require substantial mounting space.
A need, therefore, exists for a relatively simple, easily manufactured relay assembly of subminiature size having sufficient amperage rating to be employed in a wide variety of sequence control systems or safety control systems. Preferably, such a relay would take the form of a double pole, double throw, latched, two positioned, double solenoid relay which requires positive actuation to engage the movable contacts with either of two other pairs of contacts.